Electrochemical printing systems have been designed that are particularly suited to the manufacture of components for micro-electromechanical systems. For example, in U.S. Pat. No. 7,615,141, to Schwartz et al., which is hereby incorporated by reference in its entirety, an electrochemical micro-manufacturing system and method is disclosed that has a printer head that expels a jet of electrolyte towards a conductive substrate to facilitate electrochemical deposition onto the substrate or removal of material from the substrate. The electrochemical printing system disclosed in Schwartz applies a current or voltage across the electrode and the conductive substrate to deposit a material thereon using well-known electrolytic deposition processes.
However, in many applications it is desirable to electrochemically deposit a material onto a substrate without connecting the substrate directly to an electrochemical system. For example, it may be desirable to deposit (or etch) a large plurality of items without having to individually apply suitable attachment means to permit conventional electrodeposition onto the item.
Bipolar electrochemistry involving spatially segregated, equal and opposite reduction and oxidation on an electrically floating conductor, is an area of electrochemistry that has gained increasing attention in recent years. The driving force for bipolar electrochemistry is the ohmic potential variation in solution that forms during the passage of current in an electrochemical cell. When there is an appreciable ohmic potential drop through solution, and a conductor is in that potential gradient, the path of least resistance for current flow can sometimes be through the conductor via bipolar electrochemistry.
Electrochemical deposition and electrochemical etching processes are among the areas of active research in this new breed of engineering-oriented bipolar electrochemistry applications. For example, in U.S. Pat. No. 6,120,669, to Bradley, which is hereby incorporated by reference in its entirety, a bipolar electrochemical process for growing metal interconnects or wires between electrically isolated spheres or other particles using spatially coupled bipolar electrochemistry is disclosed. However, the system disclosed in Bradley is not suitable for precision electrodeposition of materials onto a conductive substrate, or precision etching of materials from a conductive substrate.